The overall objective of this proposal is to continue and extend our studies of the physiology, taxonomy and phylogeny of the obligately aerobic Gram negative bacteria, particularly those belonging to the genus Pseudomonas and related genera. The taxonomic studies will include the phenotypic analysis of a large number of strains, using approximately 180 nutritional, biochemical and morphological traits as differential characters. An improved system for the systematic identification of species will be sought. The phylogenetic relationships among the species studied will be explored by the use of DNA-DNA hybridization among a number of selected strains. DNA- ribosomal RNA hybridization will also be continued with representative strains of different species and genera belonging to different DNA homology groups. Evidence of phylogenetic relationship based on immunological and amino acid sequence analyses of homologous proteins and isofunctional enzymes will be compared with other types of evidence (overall phenotypes, DNA-DNA and DNA-RNA homologies). The immunological data will also be evaluated in terms of known protein sequences. Physiological and biochemical studies of some metabolic pathways will be continued.